Vacuum spring construction



Dec. 9, 1969 B. J. FINN ET AL VACUUM SPRING CONSTRUCTION Filed March 12.1968 3 Y mm m m N M .m E I 4 m" f A a] d. a 5

BY H/an United States Patent 3,482,832 VACUUM SPRING CONSTRUCTIONBernard J. Finn, Huntington Woods, and Alan I. Manmngs, Southfield,Mich., assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Filed Mar. 12, 1968, Ser. No. 712,441 Int. Cl.B60g 11/56 U.S. Cl. 269-34 8 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to springs and more particularly to springconstructions especially adapted for vacuum energization.

The present invention is concerned primarily with improvements in vacuumsprings of the type shown in US. Patent No. 3,106,387, Francis, entitledVacuum Spring Construction, assigned to General Motors Corporation. Inthe indicated patent, there is disclosed a vacuum spring of the piston,cylinder and diaphragm type wherein the side wall depth of the piston issignificantly less than the extended length of the diaphragm. In orderto prevent radial inward collapse of a portion of the diaphragm when thepiston is in an extended position, a helical spring of approximately thesame diameter as the inner diameter of the piston is disposed bteweenthe opposed end walls of the piston and cylinder under light compressionso that as the piston moves to the extended position, successiveindividual coils of the spring arrest radial inward deflection of theotherwise unsupported portion of the diaphragm. While this arrangementis, within limits, effective for the intended purpose, as the degree ofthe extension of the piston increases, the vertical gap between eachcoil of the spring necessarily increases with the result that localizedsupport of the diaphragm progressively diminishes.

An object of the present invention is to provide a vacuum spring of thepiston, cylinder and diaphragm type in which radial support of thediaphragm throughout the total range of movement piston is complete anduniform.

A further object is to provide an arrangement of the stated character inwhich the piston element is provided with a normally nested telescopingsleeve having resilient means associated therewith operative toyieldably displace the sleeve to a predetermined extended positionrelative to said piston.

Another object is to provide a contsruction of the stated character inwhich the sleeve and resilient means associated therewith form anintegral homogeneous unit.

The foregoing and other objects, advantages and features of theinvention will become more readily apparent as reference is had to theaccompanying specification and drawings wherein:

FIGURE 1 is a sectional elevational view, illustrating the relationshipof parts in a collapsed position;

FIGURE 2 is a fragmentary view similar to FIGURE 1, illustrating therelationship of parts in extended position; and

3,482,832 Patented Dec. 9, 1969 FIGURE 3 is a view looking in thedirection of arrows 3-3 of FIGURE 1.

Referring now to the drawings, there is shown a vehicle springconstruction in which a conventional coil spring 2 is arranged incompression between a sprung portion 4 and an unsprung portion 6, with avacuum spring unit 8 disposed in parallel relation to the coil spring 2and arranged so that energization thereof (introduction ofsubatmospheric pressure) acts in opposition to the coil spring. It willbe understood, however, that the arrangement shown is for illustrativepurposes only and that the spring unit 8 may equally well be arranged inopposite relation, i.e., to augment the elastic support provided byspring 2, or may be utilized independently.

Spring unit 8 includes an inverted cup-shaped cylinder 10 having aflange 12 secured at its lower open end to sprung portion 4 by bolts 14.Reciprocably disposed in cylinder 10 is a shallow cup-shaped piston 16having an annular side wall 18, the diameter of which is substantiallyless than the internal diameter of the side wall 20 of the cylinder. Arelatively thin walled flexible diaphragm 22 overlies the bottom wall 24of piston 16, spans the annular gap 26 between the piston and cylinderside walls, and has its outer perimeter secured between cylinder flange12 and the adjacent sprung portion 4. The cavity 28 between the pistonand cylinder is subjected to subatmospheric pressure from a convenientsource, not shown, via passage 30. When so energized, as the vacuumlevel in the cavity 28 increases, atmospheric pressure acting on thebottom wall of the piston 16 exerts an upward force on a rod 32connected at its upper end to piston 16 by clevis structure 34. Sincethe lower end 36 of rod 32 is pivotally connected at 38 to the unsprungportion 6, the sprung and unsprung portions 4 and 6 are caused to movetoward each other until the force of spring 2 balances the opposingforce of spring unit 8.

Since utilization of a vacuum spring, either alone or in conjunctionwith other springs, frequently involves application requiring pistonexcursion significantly greater than the side wall depth thereof,according to the principal feature of the invention, means are providedto assure radial support of that portion of the diaphragm not in contactwith either the cylinder wall or the piston wall. To this end, arelatively thin walled sleeve member 40 is disposed within piston 16.Sleeve member 40 is dimensioned to provide free telescoping movementrelative to the piston side wall and includes integral spring portions42 in the form of preformed accordion pleats 44 terminating inattachment legs 46 secured to the bottom wall of piston 16 by clips 48.As seen in the drawing, when the piston 16 is in a totally collapsedposition within cylinder 10, the upper flanged end 50 of the sleeveabuts the cylinder top wall and displaces the sleeve to a fully nestedposition within the piston against the resilient force of springportions 42. As the piston moves downwardly, spring portions 42progressively telescopingly displace sleeve 40 to a position axiallyjuxtaposed with the upper end of the piston and thereby form a secondarypiston side wall capable of providing radial support for the diaphragm.

To prevent excessive axial displacement of the sleeve 40, the accordionpleated spring portions 42 thereof are preformed so that their relaxedstate is just sufficient to totally displace the sleeve from the piston.With continued downward movement of the piston and sleeve, the diaphragm22 progressively peels off the cylinder wall unto not only the entirevertical wall of the piston wall but also the entire vertical wall ofthe sleeve. Thus, in spite of the fact that the piston is relativelyshallow, vertical excursion thereof is accommodated without ultimateloss of radial support of the diaphragm.

According to another feature of the invention, the sleeve 40 ispreferably formed of polypropylene or other polymer material which notonly exhibits corrosion free characteristics but also displays flexiblehinge properties enabling formation of both the sleeve portion and theresilient portion in a homogeneous structure. It will, of course, beapparent that the portion of sleeve 40 engaged by diaphragm 22 issubjected to uniform radial pressure around its entire circumference,and therefore relies on hoop compression properties rather than heavyphysical structure thereby enabling utilization of relatively light thinwall material.

While but one embodiment of the invention has been shown and described,it will be apparent that other changes and modifications may be madetherein.

We claim:

1. In a vacuum energized spring, a cup-shaped piston connected to anopposed cup-shaped cylinder by a rolling lobe diaphragm, said pistonhaving a side wall depth less than the extended length of saiddiaphragm, a sleeve telescopeably movable from a nesting position withinsaid piston to an axially juxtaposed extended position, and resilientmeans urging said sleeve out of said nested position, whereby uponmovement of said piston to an extended position relative to the end wallof said cylinder said sleeve moves out of said nested position toestablish a secondary side wall axially adjacent said piston side wallpreventing radial inward collapse of said diaphragm.

2. The invention of claim 1 including means for limiting the extendedposition of said sleeve.

3. The invention of claim 1 wherein said piston and said resilient meansform an integral unit.

4. The invention of claim 3 wherein said unit is formed of thin wallplastic material with the resilient means portion thereof preformed toyieldably collapse in accordion fashion,

5. The invention of claim 4 wherein said resilient means in its extendedrelaxed form occupies substantially the same vertical space as the sideWall depth of said piston.

6. The invention of claim 5 including means for anchoring the end ofsaid resilient means on the base of said piston.

7. The invention of claim 6 wherein said resilient means portioncomprises circumferentially spaced segments including accordion pleatedvertical portions and horizontal attachment portions.

8. The invention of claim 7 including a circumferential lip on the endof said sleeve opposite said resilient portion extending radially beyondthe side wall of said piston.

References Cited UNITED STATES PATENTS 3,003,758 10/1961 Francis 267343,106,387 10/1963 Francis 26734 JAMES B. MARBERT, Primary Examiner

